A door that only needs one key but has two to open it:
A door has an object called backup key.
The Corridor is a room.
The Private Study is a room.
The red door is east of the Corridor and west of the Private Study. The red door is a door. the red door is lockable and locked. The description of the red door is "Leads from the upstairs corridor into the private study."
The Brass Key unlocks the red door. It is in the corridor.
The backup key of the door is the white key. It is in the corridor.
Instead of unlocking a door with the backup key of the noun:
Now the noun is unlocked;
say "You unlock the door using its spare key."
Instead of locking a door with the backup key of the noun:
Now the noun is locked;
say "You lock the door using its spare key."Each door is given a property called backup key. Then when a person trys to unlock/lock the door with that key, it forces the door to do so.
You can even have a skeleton key using this code:
[code]A skeleton key is a kind of thing.
The Skull Key is a skeleton key.
Instead of unlocking a door with a skeleton key:
Now the noun is unlocked;
say “You unlock the door with a skeleton key.”
Instead of locking a door with a skeleton key:
Now the noun is locked;
say “You lock the door with a skeleton key.”[/code]